1. Field of the Invention
The present invention relates to a rotation sensor for detecting rotation of a rotating body, which is used in, for example, an engine or a transmission of an automobile.
2. Description of the Related Art
FIG. 44 is a front sectional view illustrating a related-art rotation sensor 1 disclosed in Japanese Patent Application Laid-open No. 2012-2564 (FIGS. 1, 2, and 4 to 12).
The rotation sensor 1 is inserted into an opening of a housing 10 including a rotary shaft 11 housed therein so as to be mounted to the housing 10.
A plurality of convex portions 12 made of a ferromagnetic material such as iron are provided on an outer circumferential surface of the rotary shaft 11 as a rotating body such as a connecting shaft connected to a crankshaft of an engine or the crankshaft so as to be arranged at intervals in a circumferential direction of the rotary shaft 11.
The rotation sensor 1 for detecting rotation of the rotary shaft 11 includes a case 2, a pair of lead frames 3X and 3Y, a magnetic detection section 7, an internal filling resin 8, and an exterior resin 9. The case 2 is provided at a distance from a surface of the convex portion 12, and includes a bottom surface portion 2a and a side surface portion 2b. The side surface portion 2b defines an internal space having an opening 2c in cooperation with the bottom surface portion 2a. One end of each of the lead frames 3X and 3Y is inserted into the internal space of the case 2 through the opening 2c, whereas another end thereof protrudes externally from the case 2. The magnetic detection section 7 is provided to distal ends of the lead frames 3X and 3Y so as to be electrically connected to the lead frames 3X and 3Y. The internal filling resin 8 is filled into the internal space of the case 2. The exterior resin 9 covers the opening 2c of the case 2.
A positioning portion 3Xe of the lead frame 3X and a positioning portion 3Ye of the lead frame 3Y are held in contact with an opening circumferential edge portion 2d of the case 2. In this manner, a height position of the magnetic detection section 7 inside the case 2 is determined.
The magnetic detection section 7 includes an in-sensor magnet 5 and an integrated circuit (IC) 4 that is magnetic detection means. The IC 4 includes a detection element such as a hall element and a signal processing circuit.
In the rotation sensor 1, the IC 4 generates a signal in accordance with a change in magnetic field of the in-sensor magnet 5 by the rotation of the rotary shaft 11 having the convex portions 12 made of the magnetic material.
The above-mentioned rotation sensor 1 is manufactured in the following steps as shown in FIGS. 4 to 10 of Japanese Patent Application Laid-open No. 2012-2654.
First, a lead-frame coupled body including the lead frames 3X and 3Y and a coupling portion for connecting the lead frames 3X and 3Y to each other is made of a metal plate having a rectangular shape.
Next, the magnetic detection section 7 is provided to an end of the lead-frame coupled body (first step).
Thereafter, the lead-frame coupled body and the magnetic detection section 7 are inserted into the internal space of the case 2 through the opening 2c of the case 2 (second step).
Thereafter, the internal space of the case 2 is filled with the internal filling resin 8 that is a mold resin (third step).
Next, after the internal filling resin 8 is cured, the coupling portion is removed so as to separate the lead frames 3X and 3Y from each other (fourth step).
Finally, a semi-product including the lead frames 3X and 3Y and the magnetic detection section 7 that are assembled inside the case 2 is placed inside a die (not shown) for the exterior resin 9. By molding, a connector housing for external connection and a sensor exterior part are formed on the case 2, and the opening 2c of the case 2 is covered with the exterior resin 9.
In the related-art rotation sensor 1, the internal space of the case 2 is filled with a large amount of the internal filling resin 8. A material to be used as the internal filling resin 8 is generally an epoxy resin that is expensive. Thus, there is a problem in that manufacturing costs increase.
Further, in the manufacturing of the rotation sensor 1, most attention needs to be paid to the arrangement of the magnetic detection section 7 in a predetermined dimensional position. In handling, for inserting the magnetic detection section 7 into the case 2, the pair of lead frames 3X and 3Y or the magnetic detection section 7 is inevitably required to be held. Therefore, particular attention is required to be paid so that the lead frames 3X and 3Y are not deformed. Therefore, there is another problem in that workability is low.